using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(ProcessEpocTime(1632489907280));

        Console.WriteLine(ProcessEpocTime(1650391805000000));

    }

    public static string ProcessEpocTime(long microSecs)

    {

        long milliSecs = (long)microSecs / 1000;

        DateTimeOffset utc = DateTimeOffset.FromUnixTimeMilliseconds(milliSecs).UtcDateTime;

        return utc.ToString("yyyy-MM-ddTHH:mm:ss.fffZ");

    }

}